Hydrodesulfurization of hydrocarbon oils



Aug. 25, 1959 N. E. PEERY HYDRODESULFURIZATION OF HYDROCARBON OILS FiledNov. 16, 1956 INVENTOR:

r ituhlinmw NORMAN E"PEERY United States Patent O HYDRODESULFURIZATION FHYDROCARBON OILS Norman E. Peery, San Francisco, Calif., assign'or toShell Development Company, New York, N .Y., a corporation of Delaware iApplication November 16, 1956, Serial No. 622,575

Claims. (Cl. 208-213) This invention relates to the liquid phasehydrodesul` fui-ization of sulfur containing hydrocarbon oils ofwhatever nature. More specifically, it -relates to ahydrodesulfurization process providing improved heat economy and processadvantages.

Nearly all hydrocarbon oils ranging from light distillates of the natureof gasoline and light naphthas up to heavy gas oils contain small toappreciable quantities of sulfur compounds and this is especially thecase with oils derived from petroleum, oil shales and tar sands. It isdesirable to remove the sulfur from such materials and this is done inthe few cases where the operation is economically feasible.

The desulfurization of such oils is effected, or may be effected, in anyone of three ways, to wit: (l) the hydrocarbon material is treated withhydrogen and a catalyst having hydrogenation activity to convert thesulfur in the sulfur-containing compounds to hydrogen sulfide. Examplesof this are the desulfurization of various distillate oils by so-calledhydrodesulfurization with molybdena-alumina catalyst, tungsten-nickelsulfide catalyst, cobalt-molybdena catalyst; (2) treatment of the oilwith a material which decomposes only the more labile sulfur compoundsto liberate hydrogen sulfide. Examples of this are the treatment of oils(mostly straight-run oils) with bauxite or certain clays which have theproperty of decomposing such sulfur compounds as mercaptans, alkylsulfides, and alkyl disuliides to liberate hydrogen suliide without anyappreciable effect on the more resistant sulfur compounds of thethiophene type; (3) treatment of the oil with an agent which decomposesthe more labile sulfur-containing compounds as in (2) above and thenbinds the liberated sulfur in the form of a metal sulfide in thecatalyst. Examples of this are the desulfurization of oils by treatmentwith certain metals or sulfur replaceable compounds of iron, copper,molybdenum, cobalt, nickel, etc. Such desulfurization processes aregenerally less eiiicient than the first type mentioned above, but havethe advantage that the product is substantially free of liberatedhydrogen sulfide.

Some of the agents used in these desulfurization processes may beapplied in processes of either the iirst or the third type. However, themethods of operation are distinctly diierent. For example, acobalt-molybdenaalumina catalyst may be used in the presence of hydrogenin which case the sulfur compounds of the labile as well as therefractory type are largely decomposed with the liberation of hydrogensulfide. If the process period before regeneration is very short, theliberated hydrogen sulfide is largely taken up in the catalyst andretained therein in which case a product substantially free of hydrogensulfide is obtained. If the process period is extended, the sulfurcompounds continuato be decomposed but the liberated sulfur is found inthe product in the form of hydrogen sulfide and must be subsequentlyremoved. This is disadvantageous since, in most cases, it involvescooling of the product and subsequent reheating.

Thus, while processes are known by which the sulfur compounds in an oilmay be continuously converted to a more separable form (HBS), and alsoprocesses are known by which a substantially hydrogen sulde-free productmay be obtained intermittently with very frequent regeneration of asulfur absorbing agent, there is not known, as far as I am aware, anyprocess by which a substantially desulfurized product free of hydrogensulfide may be continuously obtained. I have invented such a process.

The process will be described with reference to the accompanying drawingthe sole figure of which is a ow diagram which illustrates a preferredoperation.

In the process of the invention, a finely divided metal or metalcompound capable of reacting with hydrogen sulfide under hydrogenationconditions is suspended in the oil to be desulfurized in an amount atleast stoichiometrically equivalent to the sulfur in the oil. Hydrogenis then added and the mixture is passed. down through a foraminous bedof a sulfactive hydrogenation catalyst under hydrogenation conditions,and the suspended finely divided solid containing sulfur is removed fromthe liquid effluent of the foraminous bed. In a particular ernbodimentof the invention, a linely divided alkali metal hydride is used as themetal compound capable of reacting with hydrogen sulfide.

Referring to the drawing, the oil to be processed, and which may be alight distillate of the nature of gasoline or light naphtha or may be aheavy oil such as heavy gas oil or reduced crude petroleum, isintroduced by line 1 and passed to a mixing vessel 2 wherein it isslurried with a finely divided metal or compound thereof which iscapable of absorbing or reacting with hydrogen sulfide to form thecorresponding metal sulfide. Examples of suitable materials areprecipitated iron hydroxide, copper, copper oxide, iron, certain clays,cobalt, cobalt hydroxide, nickel, nickel hydroxide, and molybdenumoxide. It may be a pure compound as, for example, nely` divided copper,or it may be applied as a thin coating on an inert material. Forexample, bentonite, fullers earth, magnesium carbonate or other Verynely divided material may be impregnated with a solution of coppernitrate and then heated in air to convert the copper nitrate to copperoxide.

A second group of effective agents consists of hydrides of the alkalimetals and the alkaline earth metals.

The amount of the material incorporated in the oil is preferably atleast stoichiometric to the expected hydrogen sulfide to be liberated,and more preferably at least stoichiometrically equivalent to the sulfurcontained in the oil. -The sulfur combining component is preferably in afinely divided state as, for instance, a powder passing a mesh sieve,but it may be even iiner, e.g. passing a 300 mesh sieve or even be ofcolloidal dimensions.

The slurry is then mixed with hydrogen from line 5, preheated, andpassed by line 3 to a reactor 4 which is provided with a hydrogenationcatalyst such as cobaltmolybdena-alumina, tungsten sulfide-nickelsulfide, molybdena-alumina, molybenum sulfide-alumina, or the like,capable of hydrogenating sulfur compounds to liberate hydrogen suldewhile at the same time being sulfactive, i.e., capable of catalyzinghydrogenation in the presence of sulfur. This catalyst, contrary to thefirst agent, is employed as a ixed bed of particles of relatively largesize, e.g., 1A; to 3A; inch pieces. The gas containing appreciableconcentration of hydrogen, eg., at least 50%, introduced into the slurryby line 5 is added in an amount at least sufficient to convert all ofthe sulfur present to hydrogen suliide and preferably in an amountequivalent to several hundred `standard cubic feet per barrel of oil,e.g., SOO-4000 s.c.f./ bbl. The temperature in the reactor 4 ismaintained between about 300 C. and about 475 C., and the pressure ismaintained suicient to maintain the oil either substantially completelyin the vapor phase or at least 60% in the Patented Aug'. 25, 1959" 3liquid phase. The pressure, depending upon the boiling range of the oiland the desired operating phase, may vary from about 1 atmosphere toover 100 atmospheres. The mixture of gas and slurry, after passingdownward through the bed of catalyst in reactor 4, is withdrawny nearthe bottom.V In the case where the oil is maintained in reactor 4 atleast 60% in the liquid phase, the efliuent lfrom the reactor is cooledand passed to a gas separator 6. The gas is recycled-by line 5 and theliquid containing the solid in suspension is passed to a separator 7which may be a liquid cyclone (e.g., a so-called hydroclone), asillustrated, or it may be a lilter, thickener, settling tank, orcentrifuge. The clear -desulfurized oil is then passed by line 8 tostorage or subsequent use.

The finely divided solid separated from the bulk of the oil by thecyclone 7 is recovered as a thickened slurry. This may be passed to awasher 9 to separate further amounts of oil. The solid is then passed byline 10 to an oxidizing or reducing converter il wherein it isreconverted to its original state with the liberation of SO2 or H2S,which is removed by line 12. The solid may then be recycled and'used inthe process. In some cases Where solid is inexpensive, the solid removedin the separator 7 may be discarded either before or after recoveringthe sulfur values.

When operating with the oil in the vapor phase in reactor 4, theeffluent vapors are iirst passed without prior cooling through one ormore cyclone separators (not shown) to recover the solids. The solidsmay be passed directly to the oxidizing or reducing converter ordiscarded and the vapors are then cooled to condense the liquiddesulfurized oil and separate it from the gas which may be recycled.

In some cases where the solid is oxidized for re-use, part of the sulfuris converted to sulfate. In this case it is desirable to leach the usedsolid 'With Water to dissolve out the metal sulfate and to precipitatethe fresh metal hydroxide from the solution by the use of an appropriatealkali.

In case the suspended material is one of the abovementioned second groupcomprising the described hydrides, the separated material is moredifcult to reconvert to a useable form and is therefore generallydiscarded, if desired, after recovering the sulfur. Thus, for example,the removed materials may be reacted with steam to liberate hydrogensulfide which can be separately collected.

The simultaneous use of the two separate materials in the mannerindicated allows a greater removal of sulfur from the oil being treated.This is due to reaction of part of the sulfur with the suspendedmaterial and also to a shift in the desulfurization equilibrium therebymaking the fixed catalyst more effective. Thus, when using the fixedhydrogenation catalyst alone, the liberated hydrogen sulfide tends torepress further desulfurization. In fact, high partial pressures ofhydrogen sulfide in the reaction mixture limit the extent ofdesulfurization which is possible regardless of the residence time inthe reaction zone. By removing at least part of this liberated hydrogensulfide by combination with the suspended solid, the desireddesulfurization is favored. It is also found that when treating manyoils using only the lixed hydrogenation catalyst the catalyst loses itsactivity in a relatively short time. Generally, a process period of notmore than about hours is possible when treating reduced crude petroleum.The finely divided and suspended sulfurgetter used in the presentprocess apparently deactivates or absorbs most of the catalyst poisonsand consequently they are no longer in a position to deactivatey theiixcd catalyst.

In some cases where the oil rate is low and the suspended matter isrelatively coarse, it is found that the lixed bed-of` catalyst graduallybecomes clogged with the iinely divided material which builds up in thecatalyst bed. While this is inconvenient when it occurs, the ditiicultycan be avoided by back washing the fixed bed `whenever the pressure dropthrough the bed indicates incipient plugging. Treated oil is thepreferred material for the back wash; however, other liquids includingWater, when the temperature is sufliciently low, can be used. While itis not essential it is advantageous to inject a stream of hydrogen intothe bottom of the reactor along with the Wash liquid. This providessuii'icient agitation that it is usually unnecessary to jiggle thecatalyst bed.

The process of the invention is not only useful for thehydrodesulfurization of hydrocarbon oils but it is also useful when itis desired to hydrogenate oils much more deeply. Thus, for instance, itis frequently desired to hydrogenate oils containing appreciableconcentration of aromatic hydrocarbons to such an extent that thearomatic hydrocarbons are also largely hydrogenated. When the oilcontains appreciable amounts of sulfur compounds, as is frequently thecase, it istfound that a substantial portion of the hydrogen used isconsumed in 4hydrogenating the sulfur compounds before hydrogenation` ofthe aromatic hydrocarbons begins. For example, wheny the total uptake ofhydrogen is 600 s.c.f./bbl. of oil, 200 s.c.f. of this rnay be utilizedonly in hydrogenating sulfur compounds. In the present process, by usinga sufficient amount of suspended metal, practically all of the hydrogenmay be consumed in the desired hydrogenation ofthe aromatic hydrocarbonswhile at the same time still obtainingV a desulfurized product. This isbelieved due to regeneration of hydrogen according to the equation Inthe above, the process has been described in a preferred embodiment inwhich the finely. ydivided agent is suspended. in all of the feed andthe suspension is trickled;

downward through a foraminous bed of the large catalyst particles underhydrogenation conditions. It will be appreciated that the finely dividedmaterial may be suspended in only a fraction or portion of the oil andthis may be passed through the catalyst bed along with the main body ofthe oil.

Example Luxmass (mostly ferrie hydroxide) obtained as a by- .productfrom bauxite in the recovery of alumina as sodiumy aluminate is iinelyground and then screened -to rejectall material retained on a standard300 mesh sieve. This material is added in various amounts up to 62 gramsper liter to a Mexican gas oil having the following inspection` data andthoroughly agitated to form homogenous suspensions:

Sulfur, percent wt. 3.10 Acid value, mg. KOH/g 3.2 Ash, percent wt.0.001 Diesel index 29` ASTM distillation:

I.B.P.- C. 248 10% vo1.- C. 267" 20% vol.- C. 274 30% Vo1.- C. 279 40%vo1.- C. 286V 50% vol.- C. 293 60% vol.- C. 301 70% vol. C. 311 vol.- C.325 vol.-- C; 343' vol,.- C. 354. F.B.P.- C.

Elementary analysis:

C-percent wt. 84.86 H-percent wt. 11.98. S-percent wt. 3.10 O--percentwt. 0.04

yb l-percent wt. 0-.02

QoL-ieri Each suspension is passed along with hydrogen through a heatedcoil of such dimensions that the ilow is turbulent, wherein it is heatedto a temperature of 375 C. The suspension, along with the hydrogen, isthen passed downward through a fixed bed of 8 x 8 mm. catalyst pelletsconsisting of 0.8% Co and 6.5% Mo as sulfides deposited in an activatedSurinam bauxite carrier. The throughput rate is 5.06 kg./l./hr.; thetemperature and pressure are 375 C. and 50 atm., respectively. Theamount of hydrogen supplied is adjusted such that the exit gas amountsto 49 standard cubic meters of hydrogen per metric ton of product. Theproduct issuing from the Abottom of the reactor is cooled, and theliquid separated from the gas. The pressure is released on the liquidwhich releases a further amount of gas and the liquid is thencentrifuged to separate suspended solids.

When operating in this manner without the suspended Luxmass, thedisposition of the sulfur in percent is as follows:

Sulfur retained in the oil percent-.. 60.9 Sulfur removed in gas do 7.2Sulfur released from oil -do 17.5 Sulfur dissolved in oil do 14.4Solubility constant of HZS at 1 atm. and 20 C. 4.4

As the amount of Luxmass suspended in the feed is increased, the sulfurcontent of the product and of the recycle gas decreased until whensufficient Luxmass is used to combine with all of the liberated H28 theproduct and recycle gas are substantially sweet.

When using colloidal copper or nickel in place of the Luxmass theresults are similar, but the recovery of the metal is more diiicult.

I claim as my invention:

l. A process for the hydrodesulfurization of a hydrocarbon oil whichcomprises suspending in the oil to be desulfurized a iinely dividedmetal compound capable of reacting with hydrogen sulde under thesubsequent hydrogenation conditions, in an amount at leaststoichiometrically equivalent to the sulfur in the oil, adding hydrogenand continuously passing the mixture down through a xed, foraminous bedof a sulfactive hydrogenation catalyst under hydrogenation conditions,and separating suspended finely divided solid containing sulfur from theeffluent of said foraminous catalyst bed.

2. A process for the hydrodesulfurization of a hydrocarbon oil whichcomprises suspending in the oil to be desulfrized a finely divided metalcompound capable of reacting with hydrogen sulfide under the subsequenthydrogenation conditions, in an amount at least stoichiometricallyequivalent to the sulfur in the oil, adding hydrogen and continuouslypassing the mixture down through a lixed, foraminous Ibed of asulfactive catalyst under hydrogenation conditions and at a pressuresuiiciently high that at least of the oil remains in the liquid phase,and separating suspended iinely divided solid containing sulfur from theeiiluent of said forarninous catalyst rbed.

3. A process for the hydrodesulfurization of a hydrocarbon oil whichcomprises suspending in the oil to be desulfurized a linely dividedmetal oxide capable of reacting With hydrogen sulfide under thesubsequent hydrogenation conditions in an amount at leaststoichiometrically equivalent to the sulfur in the oil, adding hydrogenand continuously passing the mixture down through a fixed, foraminousbed of a sulfactive catalyst under hydrogenation conditions, separatingsuspended finely divided sulided metal oxide from the eiiluent of saidforaminous catalyst bed, reconverting the: sulfided metal oxide to theoxide and recycling the same.

4. A process for the hydrodesulfurization of a hydrocanbon oil whichcomprises suspending in the oil to be desulfurized a finely dividedmetal capable of reacting with hydrogen sulfide under the subsequenthydrogenation conditions in an amount at least stoichiometricallyequivalent to the sulfur in the oil, adding hydrogen and continuouslypassing the mixture down through a fixed foraminous bed of a sulfactivecatalyst under hydrogenation conditions, separating suspended finelydivided sulded metal from the effluent of said fora-minous catalyst bed,reconverting the sulfded metal to the metal and recycling the salme.

5. A process for the hydrodesulfurization of a hydrocarbon oil whichcomprises suspending in the oil to be desulfurized a finely dividedalkali metal hydride in an amount at least stoichiometrically equivalentto the sulfur in the oil, adding hydrogen, and continuously passing themixture down through a fixed, foranlinous bed of a sulfactivehydrogenation catalyst under hydrogenation conditions, and separatingsuspended sulfided alkali metal hydride from the eiiiuent of saidforaminous bed.

References Cited in the le of this patent UNITED STATES PATENTS1,608,339 Ridge et al Nov. 23, 1926 1,954,843 Schaad Apr. 17, 19342,398,919 Byrns Apr. 23, 194.6 2,559,457 Montgomery et a1 July 3, 19512,723,943 McAfee Nov. 15, 1955

1. A PROCESS FOR THE HYDRODESULFURIZATION OF A HYDROCARBON OIL WHICHCOMPRISES SUSPENDING IN THE OIL TO BE DESULFURIZED A FINELY DIVIDEDMETAL COMPOUND CAPABLE OF REACTING WITH HYDROGEN SULFIDE UNDER THESUBSEQUENT HYDROGENATION CONDITIONS, IN AN AMOUNT AT LEASTSTOICHIOMETRICALLY EQUIVALENT TO THE SULFUR IN THE OIL, ADDING HYDROGENAND CONTINOUSLY PASSING THE MIXTURE DOWN THROUGH A FIXED, FORAMINOUS BEDOF A SULFACTIVE HYDROGENATION CATALYST UNDER HYDROGENATION CONDITIONS,AND SEPARATING SUSPENDED FINELY DIVIDED SOLID CONTAINING SULFUR FROM THEEFFLUENT OF SAID FORAMINOUS CATALYST BED.